1. Field of the Present Invention
The present invention is a pump dispenser for viscous fluids, namely creams, lotions, and the like.
2. Description of the Prior Art
The prior art shows a variety of dispensers for fluid masses which comprise a generally tubular container with a pumping mechanism at one end and a take-up piston at the other. In such dispensers, the pumping mechanism is adapted to dispense the product from the container. As product is removed from the container which holds it, the take-up piston is moved by atmospheric pressure towards the pumping mechanism to insure that the fluid product and any associated reservoir in the pumping mechanism do not develop unwanted voids or open spaces which would interfere with the desired dispensing action on subsequent uses of the dispenser. One approach to the design of an appropriate pumping mechanism for one end of such containers is to provide a container body part which is resiliently compressible to effect a decrease in voIume of a pumping chamber so as to cause the dispensing of product from the container. Examples of devices which use such an approach are U.S. Pat. Nos. 3,088,636; 3,361,305; 3,768,705; 4,154,371; 4,402,431; 4,413,759; 4,442,958; 4,474,313; and 4,533,069.
An alternative approach to the design of an appropriate pumping mechanism for tubular containers having a take-up piston at its opposite end is to provide a pumping dispenser having movable, rigid members which effect an appropriate volume reduction in a reservoir to dispense product therefrom. The following patents have been noted as following this approach:
U.S. Pat. No. 4,301,948 to J. Czech illustrates a pumping mechanism which comprises a head member in the form of a substantially cylindrical cap which is slidely supported on an outer side wall surface of the container. Movement of the head member towards the tubular container effects a reduction in a pump chamber containing the product to effect dispensing of the product through a suitable outlet in the head member.
U.S. Pat. No. 4,323,175 to J. Eckert illustrates a dispenser having a delivery device on the upper side of a supply container, transverse to the main direction in which the supply container extends. This delivery device has a cylinder space in which is arranged a displacement piston which is adapted to be displaced axially.
U.S. Pat. No. 4,485,943 to J. Czech shows a dispenser which utilizes a spring-biased piston to effect an appropriate reduction in the volume of a pump chamber. The path of egress of the material from the pump chamber to the outlet first lies in a direction lateral to the path of travel of the piston and thence parallel to the path of travel of the piston but laterally displaced therefrom.
U.S. Pat. Nos. 4,511,068 to J. Bossina and 4,598,843 to D. D. Foster et al. both show the use of spring-mounted pistons to effect removal of viscous product from the type of tubular container described before. In both cases the product is dispensed through outlet means in the piston structure initially in the direction that is parallel, and coaxial, with the path of travel of the piston, and the lateral dimensions of the piston are substantially the same as the inner diameter of the tubular container. In other words, the lower surface of the delivery piston at its circumferential portions makes sealing contact with the inner walls of the tubular container.